1. Field of the Invention
The present invention relates to a nonvolatile memory device including a nonvolatile memory and a controller unit.
2. Description of Related Art
A NAND flash card is a kind of nonvolatile memory device that enables rewriting, prevents data erasing when the power is turned off and also enables batch erasing. Since NAND flash cards enable downsizing of circuits and thus are suitable for providing large capacity, they have broadly been used as storage devices for digital cameras, portable music players and mobile phones, etc., in recent years.
A NAND flash card includes a NAND flash memory and a controller LSI for the NAND flash memory (see, for example, Japanese Patent Application Laid-Open Publication No. 2006-48777).
The NAND flash memory includes a logic section, an analog section and a memory cell array, and the controller LSI includes a logic section and an analog section.
Here, in the NAND flash memory and the controller LSI, the respective analog sections generate regulator voltages necessary for the respective logic sections, detection signals (reset signals) indicating that an externally-supplied power supply voltage has reached a minimum guaranteed voltage, and operation clocks, and supply the regulator voltages, the detection signal and the operation clocks to the respective logic sections.
Accordingly, the analog section of the NAND flash memory and the analog section of the controller LSI have configurations that provide similar circuit functions (e.g., their respective voltage detecting functions), causing problems in that: the circuit sizes are increased; and also if there is an error in level of detection of a minimum guaranteed voltage between the two voltage detection functions, either the NAND flash memory or the controller LSI will not operate due to such detection error, resulting in the state in which the NAND flash card does not normally operate.